Congenital diaphragmatic hernia (CDH) is associated high mortality and morbidity, mainly in those cases with severe forms where there are extremely reduced lung volumes, liver herniation and decreased abnormal pulmonary vascularization. Fetal endoscopic tracheal occlusion performed between 26 and 30 weeks (standard FETO) has been shown to increase fetal pulmonary size and vascularity, and to improve infant survival in isolated severe CDH. Fetal pulmonary response followed FETO can be used to predict outcome and is dependent on the size of the fetal lung prior to the procedure.